Lens barrel, camera and portable information terminal

ABSTRACT

A lens barrel including a telescopic cylinder accommodated within a fixed cylinder, and lenses retained in the telescopic cylinder. The lens barrel includes lens retaining frames to retain at least one of the lenses and a lens driving device to drive the lens retaining frames so as to drive the lenses along a longitudinal axis of the telescopic cylinder between a collapsed position in which one portion of the lenses is stored in the fixed cylinder and an extended position in which one portion of the lenses is extended out of the fixed cylinder toward a photographing subject. The lens barrel further includes a retractable lens that is retracted into the fixed cylinder through an opening in a wall of the fixed cylinder when the telescopic cylinder is in the extended position, and a retractable lens retaining frame to retain the retractable lens. The lens barrel includes an impact preventing member so that if the lenses are in the extended position and an external impact is received by the lens barrel, the impact preventing member abuts against one of the lens retaining frames to prevent the lens retaining frames from moving to the collapsed state and contacting the retractable lens retaining frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit ofpriority under 35 U.S.C. §120 from U.S. Ser. No. 11/188,691, whichclaims the priority benefit of Japanese Patent Application No.2004-217927, filed on Jul. 26, 2004. In addition, the presentapplication is related to the U.S. patent application entitled “LensBarrel, Camera and Mobile Information Terminal” application Ser. No.11/188,864), which claims the benefit of priority to each of JapanesePatent Application 2004-217539 filed on Jul. 26, 2004, Japanese PatentApplication 2005-044909 filed on Feb. 22, 2005, and Japanese PatentApplication 2005-127226 filed on Apr. 25, 2005. In addition, the presentapplication is related to PCT Application No. PCT/JP2005/014002(WO2006/011621 A1, Attorney Docket Number 274053US), which claims thebenefit of priority to Japanese patent Application No. 2004-217924 filedon Jul. 26, 2004. In addition, the present application is related to theU.S. patent application entitled “Optical System Apparatus, Camera andPortable Information Terminal Apparatus” (application Ser. No.11/188,872), which claims the benefit of priority to Japanese PatentApplication No. 2004-217932, filed on Jul. 26, 2004, and Japanese PatentApplication No. 2004-348005, filed on Dec. 1, 2004. The contents of eachof the above-identified applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens barrel that collapses, storeslens groups therein when not in use, and extends the lens groups topredetermined positions when photographing. More particularly, thepresent invention relates to a lens barrel, a camera, and a portableinformation terminal apparatus including a lens barrel suitable for azoom lens unit that can change the focal distance by relatively moving aplurality of lens groups.

2. Discussion of the Background

With improvement in high performance of a photographing lens such as azoom lens unit that is capable of changing the focal distance and indownsizing according to the user's demand as to an image pickupapparatus such as a digital camera, there are increasing types of imagepickup apparatus employing a so-called collapsing photographing lensunit in which lens cylinders are stored within a body of the imagepickup apparatus when photographing is not carried out. Furthermore,since not only simple reduction in dimensions, but also furtherreduction in thickness of the image pickup apparatus are also demanded,it is now important to reduce the thickness of the lens barrel portionin a collapsed state to the minimum limit.

As a technology to cope with the demand for reduction in thickness ofthe image pickup apparatus, a collapsible construction has been used, inwhich the lens cylinders are stored into the body of the image pickupapparatus when the photographing is not carried out and in which a partof the lenses is evacuated from an optical axis of the lenses inphotographing, when the lens cylinders are collapsed and stored. Such atechnology is disclosed, for example, in JP-A 2003-315861 and in JP-A2003-149723. According to the structures disclosed in these Japaneseunexamined patent application publications, since a part of the lensesis evacuated from the optical axis when the lens cylinders are stored,the dimension of the entire lenses in a direction of the optical axiscan be reduced in the collapsed state, so that the thickness of theimage pickup apparatus can be reduced.

However, in the structures disclosed in JP-A 2003-315861 and JP-A2003-149723, the position of the lens evacuated from the optical axis issubstantially within that lens cylinder which has the maximum outerdiameter. Therefore, the lens cylinders contribute to reduction inthickness of the image pickup apparatus when the lenses are stored, butthe outer diameter of the lens barrel increases. When compared with acase where the lens is not evacuated from the optical axis, since theouter diameter of the lens cylinders increase, the dimensions of thelens cylinders, in particular, the dimensions of the lens cylinders asviewed in a plane orthogonal to the optical axis increase. As a result,there arises a problem that the dimensions of the image pickupapparatus, in particular, the dimension as viewed from a front side ofthe image pickup apparatus increases.

On the other hand, in a lens barrel in which some of the lenses areevacuated from the optical axis when the lens barrel is stored, if anexternal impact is applied to the lens barrel as in a case ofunintentional drop of a camera, a portable information terminal, or thelike including the lens barrel, or collision of the camera, the portableinformation terminal, or the like against another object, a lens frameof the lens barrel at an object side is forced into a collapsed statewhen the lens to be evacuated is on the optical axis. This causes aspecific problem of making the retractable lens retaining frame subjectto damage.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovementioned deficiencies in the prior art. Thus, one object of the presentinvention is to provide a lens barrel, which is prevented from beingdamaged by external impact such as a drop of the lens barrel, thedimension of which in the direction of the optical axis when the lens isstored can be reduced, the dimension of which in a plane orthogonal tothe optical axis can be reduced, and the dimensions of the imagingdevice included in which can be reduced, and to provide a camera usingthis lens barrel, and a portable information terminal using this lensbarrel.

To achieve the above object, the present invention provides lens barrel,comprising: (1) a telescopic cylinder configured to be accommodatedwithin a fixed cylinder; (2) a plurality of lenses configured to beretained in the telescopic cylinder; (3) a plurality of lens retainingframes, each lens retaining frame configured to retain at least one lensin the plurality of lenses; (4) a lens driving device configured todrive the plurality of lens retaining frames so as to drive theplurality of lenses along a longitudinal axis of the telescopic cylinderbetween a collapsed position in which at least one portion of theplurality of lenses is stored in the fixed cylinder and an extendedposition in which the at least one portion of the plurality of lenses isextended out of the fixed cylinder toward a photographing subject; (5)at least one retractable lens configured to be retracted into the fixedcylinder through an opening in a wall of the fixed cylinder when thetelescopic cylinder is in the extended position; (6) a retractable lensretaining frame configured to retain the at least one retractable lens,wherein the lens driving device is configured to drive the retractablelens retaining frame so that the retractable lens is retracted into thefixed cylinder when the telescopic cylinder is in the extended position;and (7) an impact preventing member, wherein, if the plurality of lensesare in the extended position and an external impact is received by thelens barrel, the impact preventing member is configured to abut againstat least one of the plurality of lens retaining frames to prevent theplurality of lens retaining frames from moving to the collapsed stateand contacting the retractable lens retaining frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view showing a structure of a main part of anoptical system device including a lens barrel according to a firstembodiment of the present invention with lens groups collapsed, as viewfrom a subject.

FIG. 2 is a perspective view showing the main part of the lens barrelshown in FIG.1, as viewed from an imaging plane.

FIG. 3 is a schematic perspective view showing a structure of a mainpart of the optical system device including the lens barrel in which alens barrier is closed, as viewed from the subject.

FIG. 4 is a schematic perspective view showing the structure of the mainpart of the lens barrel shown in FIG. 3, as viewed from the imagingplane.

FIG. 5 is a schematic perspective view of the structure of the main partof the lens barrel in a state in which the lens barrier is opened in aphotographing state with the lens groups extended, as viewed from theimaging plane.

FIG. 6 is a perspective view of the structure of the main part of thelens barrel in the photographing state with the lens groups extended, asviewed from the imaging plane.

FIG. 7 is a perspective view of a layout of a third frame, an impactpreventing member, and a fourth frame in a state in which the lensgroups are in a collapsed position, for explaining operations of thethird frame which retains the third lens group and the impact preventingmember, as viewed from the subject.

FIG. 8 is a perspective view of a layout of the third frame, the impactpreventing member, and the fourth frame for explaining operations of thethird frame, which retains the third lens group, and theimpact-preventing member in the photographing state with the lens groupsprojected, as viewed from the subject.

FIG. 9 is a vertical cross sectional view showing, in an upper half anda lower half with respect to an optical axis, main parts of the lensgroups, the lens retaining frames, and the various lens cylinders of thelens barrel in the photographing state in which the lens groups areextended, and in the collapsed state in which the lens groups areretired to be collapsed, respectively.

FIG. 10 is a schematic development elevational view showing a shape ofcam grooves formed on a second rotary cylinder in a developed state.

FIG. 11 is a schematic development elevational view showing a shape ofcam grooves formed on a cam cylinder in a developed state.

FIG. 12 is a schematic development elevational view showing a shape ofcam grooves and key grooves formed on a first liner in a developed statewith a helicoid omitted.

FIG. 13 is a schematic development elevational view showing a shape ofcam grooves and key grooves formed on a fixed frame in a developed statewith the helicoid omitted.

FIG. 14 is a side view showing a structure of the third frame and itsdrive system.

FIG. 15 is a perspective view showing the structure of the third frameand its drive system.

FIG. 16 is a back view of the third frame portion for explainingoperation of the third frame, as viewed from the imaging plane.

FIG. 17A and 17B are perspective views showing an exterior appearanceand a structure of a camera according to a second embodiment of thepresent invention as viewed from the subject, in which FIG. 17A shows astate in which a photographing lens is collapsed in a body of thecamera, and FIG. 17B shows a state in which the photographing lens isprojected or extended from the camera body.

FIG. 18 is a perspective view schematically showing the exteriorappearance and structure of the camera of FIGS. 17A and 17B as viewedfrom a user.

FIG. 19 is a block diagram schematically showing a functional structureof the camera of FIGS. 17A and 17B.

FIG. 20 is an exploded perspective view of a structure of a lens barrelportion in a state that lens groups of a camera according to a thirdembodiment of the present invention are partly protruded and a structureof a front cover of the camera in a state that a lens barrier is halfwayclosed, as viewed from the imaging plane.

FIG. 21 is an exploded perspective view of the structures in the statesshown in FIG. 20 as viewed from the subject.

FIG. 22 is a back view of the structure of the front cover of the camerafrom which an inner cover is removed, as viewed from the imaging plane.

FIG. 23 is a chart showing a state in which the lens barrier is operatedfrom an opened position to a closed position.

FIG. 24 A is a table showing a reset sequence of the lens barrel.

FIG. 24 B is a timing chart of an H signal.

FIG. 25 is a timing chart showing a storage sequence in a state in whichthe lens barrier is closed.

FIG. 26 is a flow chart showing a zoom sequence.

FIG. 27 is a timing chart showing a state from the wide angle to thetelephoto.

FIG. 28 is a timing chart showing a state from the telephoto to the wideangle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail based on preferred embodiments ofthe present invention with reference to the accompanying drawings.Wherever possible, the same reference numbers are used in the drawingsand the description to refer to the same or like parts. The presentinvention, however, is not limited to these embodiments. Within thescope of the present invention, any structure and material describedbelow can be appropriately modified.

FIGS. 1 to 16 and 20 illustrate a first embodiment of a lens barrelaccording to the present invention.

In FIGS. 1 to 16 and 20, the lens barrel includes a fixed frame 21having a fixed cylinder 21 a, a telescopic cylinder unit or telescopiccylinder attached to the fixed frame 21, and a plurality of lens groupsdisposed in the telescopic cylinder. The telescopic cylinder is movableand collapsible along an optical axis X of the plurality of lens groups.

The lens groups comprise, for example, a first lens group (lens) 11, asecond lens group (lens) 12, a third lens group (lens) 13, and a fourthlens group (lens) 14, which are disposed in the telescopic cylinder (seeFIG. 9).

The telescopic cylinder includes, for example, a first rotary cylinder22, a first liner 23, a second rotary cylinder 24, a second liner 25, acam cylinder 26, a lineally-moving cylinder 27, and a third frame 31(retractable lens retaining frame) (see FIGS. 5 and 8) for retaining thethird lens group (retractable lens) 13. As described below, the firstrotary cylinder 22 and so on are moved along the optical axis withrespect to each other with the plurality of lens groups 11 to 14. Anyshape or structure may be used instead of the telescopic cylinder. Forexample, a plurality of peripherally spaced slidable bars or bands maybe used without being limited to the cylinder shape of the telescopiccylinder.

As shown in FIG. 9, the first, second, third, and fourth lens groups 11,12, 13, and 14 are positioned from a subject (not shown) in sequence anddisposed on the optical axis X. A shutter/aperture stop unit 15 isdisposed between the second lens group 12 and the third lens group 13.The first, second, third, and fourth lens groups 11, 12, 13, and 14, andthe shutter/aperture stop unit 15 are configured to be movable in adirection of the optical axis when the telescopic cylinder is movedalong the optical direction.

To use the lens barrel for image forming apparatuses or optical devicessuch as digital cameras or the like, as described hereinafter, forexample, a solid-state image-sensing device 16 comprising a CCD(charge-coupled device) or the like is disposed adjacent to the side ofan image forming plane of the fourth lens group 14.

Referring to FIG. 9, the first lens group 11 is attached to a firstframe (lens retaining frame) 17, and a cover glass 18 and a low-passfilter 19 are disposed adjacent to an image-receiving surface of the CCD16, if needed.

Generally, as shown in FIG. 9, the lens barrel is structured such thatthe first to fourth lens groups are movable between a collapsed positionS stored in the fixed cylinder 21 a and an extended position D extendedout of the fixed cylinder 21 a, a zooming is achieved, and at least onelens group of the first to fourth lens groups can be retracted out ofthe optical axis into a retracted position as shown at R in FIG. 9. Inthe embodiment, at least one portion of the third lens group 13 isretracted from the optical axis passing through a through hole providedin the fixed cylinder 21 a into a stored part provided in the fixedcylinder 21 a and corresponding to the retracted position as describedabove.

In regard to this, a further detailed description will be describedhereinafter.

The first lens group 11 to the fourth lens group 14 has a zoom lensfunction in which a focal distance is variable, as describedhereinafter. The first lens group 11 includes one or more lens, and isfixed to the lineally-moving cylinder 27 via the first frame 17, whichretains the first lens group 11 integrally.

The second lens group 12 includes one or more lens. A cam followerformed on a second frame (not shown) for integrally retaining the secondlens group 12 is inserted into a cam groove for the second lens group 12formed on the cam cylinder 26 shown in FIGS. 9 and 11, and engages witha linear groove 25 a of the second liner 25, and the second lens group12 is supported by the cam cylinder 26 and the second liner 25.

The shutter/aperture unit 15 includes a shutter and an aperture, and acam follower formed integrally with the shutter/aperture unit 15 isinserted into a cam groove for the shutter/aperture of the cam cylinder26 shown in FIG. 11 and is engaged with the linear groove 25a on thesecond liner 25 so that the shutter/aperture unit is supported by thecam cylinder 26 and the second liner 25.

The fixed frame 21 includes a cylindrical part (i.e. the fixed cylinder21a) having an inner surface which is formed with a linear groove and ahelicoidal cam groove along an axial direction, as shown in FIGS. 13Aand 13B. A helicoidal cam follower formed on an outer peripheral surfaceof a base portion of the first rotary cylinder 22 engages with thehelicoidal cam groove, as shown in FIG. 13C, and a key portion formed onan inner surface of a base portion of the first liner 23 engages withthe linear groove of the fixed frame of the fixed frame 21. An innersurface of the first rotary cylinder 22 is formed with a guide grooveextending along a plane transverse to the optical axis X. Engaged withthe guide groove is a follower or key which is formed to project fromthe outer peripheral surface of the first liner 23 in the vicinity ofthe base portion thereof and acts as a linear member.

An inner surface of the first liner 23 is formed with a linear groovealong the optical axis and a helicoid, in addition, the first liner 23is formed with a clearance groove in which a cam follower formed toproject from an outer peripheral surface of a base portion of the secondrotary cylinder 24 in the vicinity of the base portion is inserted.

A helicoid is formed on the outer peripheral surface of the base portionof the second rotary cylinder 24, and is engaged with the helicoid ofthe first liner 23. A cam follower formed to project from the outerperipheral surface of the second rotary cylinder 24 in the vicinity ofthe base portion engages with the linear groove formed in the innerperiphery of the first rotary cylinder 22 through the clearance grooveof the cam follower on the first liner 23. A key portion formed toproject from the outer peripheral surface of the base portion of thesecond liner 25 engages with the linear groove provided on the innerperipheral surface of the first liner 23.

An inner surface of the second rotary cylinder 24 is provided with aguide groove along a plane transverse to the optical axis X, a followeror key provided to project from the outer peripheral surface of thesecond liner 25 is engaged in the guide groove of the second rotarycylinder 24. With such a structure, the second liner 25 moves with thesecond rotary cylinder 24 in the movement along the optical axis X,while the second rotary cylinder 24 is rotatable relative to the secondliner 25.

The cam cylinder 26 fitted to the inner periphery of the second liner 25is configured in such a manner that an engaging projection formed on theouter peripheral surface of the base portion is fitted to and engagedwith the base portion of the second rotary cylinder 24 so as to rotateintegrally with the second rotary cylinder 24. The inner surface of thesecond liner 25 is provided with a guide groove along a surfacetransverse to the optical axis X, and a follower or key provided on theouter peripheral surface (front side) of the cam cylinder 26 engageswith the cam groove. With such a structure, the cam cylinder 26 moveswith the second liner 25 in the movement along the optical axis X, whileis rotatable relative to the second liner 25.

The base portion of the lineally-moving cylinder 27 is inserted betweenthe second rotary cylinder 24 and the second liner 25, and a camfollower is formed to project from the outer peripheral surface of thelineally-moving cylinder 27 in the vicinity of the base portion, and thecam follower engages with the cam groove formed in the inner peripheralsurface of the second rotary cylinder 24. A linear groove is formed onthe inner peripheral surface of the lineally-moving cylinder 27 alongthe axial direction, and the key portion formed on the outer peripheralsurface of the second liner 25 engages with the linear groove.

A gear portion is formed on the outer periphery of the base portion ofthe first rotary cylinder 22, the gear portion is engaged with one ormore gears which are driven by a zooming motor 51 so that a drive forceof the zooming motor 51 is transmitted to the gear portion via thegears, whereby the first lens group 11, the second lens group 12, andthe shutter/aperture unit 15 are zoomed in a predetermined manner. Thezooming motor comprises a usual DC motor in the embodiment.

Meanwhile, the cam groove on the second rotary cylinder 24 engaging withthe cam follower on the linearly-moving cylinder 27 is shown in FIG. 10.

The cam groove on the cam cylinder 26 which engages with the camfollower on the lens retaining frame of the second lens group 12 and thecam groove of the cam cylinder 26 which engages with the cam follower ofthe shutter/aperture unit 15 are shown in FIG. 11, respectively.

The cam groove on the first liner 23 which engages with the cam followerof the second rotary cylinder 24 and the straight groove on the firstliner 23 which engages with the key groove on the second liner 25 areshown in FIG. 12, respectively.

A linear groove on the fixed frame 21 engaging with the key portion ofthe first liner 23 of the fixed frame and the cam groove of the fixedframe 21 engaging with the cam follower of the first rotary cylinder 22are shown in FIG. 13, respectively.

Generally, the rotary cylinder, which is the closest position to thefixed frame and positioned on the outermost circumference is generallyscrewed onto the fixed frame through a helicoid, and the helicoid isconfigured to move the rotary cylinder at a constant speed relative tothe fixed frame. Therefore, the rotary cylinder is in a half-extendedstate out of the fixed frame in a short focal length/wide angle positionin a course in which the rotary cylinder is moved gradually from thecollapsible position through the short focal length/wide angle positionto a long focal length/telephoto position.

On the contrary, in the structure described above, the first rotarycylinder 22 adjacent to the fixed frame 21 is threaded with the fixedframe of the fixed frame 21 via the cam groove of the helicoidal shapewithout a simple helicoidal connection. The first rotary cylinder 22 ismoved completely to the maximally extended position by being driven fromthe collapsible or collapsed position to the short focal length/wideangle position. Thereafter, as shown in FIG. 13, because the subjectside end of the cam groove lies in parallel with the end surface of thefixed frame, the first rotary cylinder 22 rotates at a constant positionwithout moving along the optical axis X during driving from the shortfocal length/wide angle position to the long focal length/telephotoposition.

In addition, the third lens group 13 is retracted out of the opticalaxis X in the collapsed position, in which the lens groups are collapsedin the fixed frame 21, as shown in FIG. 9. The third lens group 13 ismoved onto the optical axis X in an extended position of the lensgroups.

As the first rotary cylinder 22 is moved from the collapsed position toshort focal length/wide angle position, it is extended toward thesubject, while rotating in an early stage of the drawing out action andwhen it reach the maximally extended position, a zoom position-detectorwhich is provided on the fixed frame 21 and comprising aphoto-reflector, photo-interrupter, leaf switch or the like, forexample, generates a zoom position-reference signal. Therefore, when thezoom position-reference signal generates, because it may be determinedthat the first rotary cylinder 22 reaches the maximally extendedposition, it is possible to initiate to move the third frame 31 onto theoptical axis X.

Consequently, a space between the second lens group 12 and the fourthlens group 14 to insert the third lend group 13 into the optical axis Xcan be secured previously by completely drawing out the first rotarycylinder 22 and the first liner 23 adjacent to the fixed frame at theearlier step of the extended action.

As described below, as soon as the first rotary cylinder 22 reaches themaximally extended position, the zoom position-reference signalgenerates, the space for inserting the third lens group is secured, andimmediately, the insertion of the third lens group is initiated.Therefore, a time from the collapsible position when an electric sourceis turned on to the short focal length/wide angle position can be veryshortened.

As described above, the retractable third lens group 13 is retained tothe third frame 31 or retractable lens retaining frame. The third frame31 retains the third lens group 13 at one end thereof, and the other endof the third frame 31 is supported by a third group main-guide shaft 32which extends substantially in parallel with the optical axis of thethird lens group 13 so as to be capable of rotating, and sliding alongthe third group main-guide shaft 32. The third frame 31 is rotatableabout the third group main-guide shaft 32 between a setting position inwhich the third lens group 13 is disposed onto the optical axis in aphotographing state, as shown in FIG. 8 and the retracted position inwhich the third lens group 13 is retracted out of the telescopiccylinder into the fixed frame 21, as shown in FIG. 2.

In the vicinity of the third lens group 13 on the side of the rotatingend of the third frame 31, a crank-shaped bent portion fordifferentiating the position of the third lens group 13 in the directionparallel with the main guide shaft between the side of the rotation axisand the side of the supporting portion, a stopper 31 a (FIG. 15) and alight-shielding strip 31 b are provided on the rotating end to projectfrom the bent portion substantially toward the rotating end.

On the optical performance, in order to lengthen a focus length in thetelephoto state, a position of the third lens group 13 in the telephotostate is in an extended position closer to the subject. However, apossible moving amount of the third frame 31 is determined by limitationof a length of the lens barrel in the collapsed state along the opticalaxis X. It is possible to maximize the focus length in the telephotostate by setting a position for retaining the third lens group by thethird frame 31 in the closest position to the subject. However, if aposition of the stopper 31 a along the optical axis sets on thegenerally same position as the third lens group 13, a length of a thirdframe sub-guide shaft 33 is longer and a size of the lens barrel in thecollapsible position becomes greater. Therefore, it is required that thestopper 31 a is set on a side of a focusing position and the third frame31 is formed into a shape having the crank-shaped bent portion.

Meanwhile, the third frame 31 may be formed from two parts and in thiscase, one is a member having the crank-shaped bent portion, the other isa member for retaining the third lens group 13. The two parts operatesintegrally by being fixed together.

As shown in FIGS. 14A and 14B, a third frame female screw member 35screwed on a third group lead screw 34 is positioned in the closestposition to an image plane of the CCD in the retracted state in whichthe third frame 31 is retracted. In this state, a compression torsionspring 37 is charged or compressed fully so as to impart constantly aclockwise moment as viewed from the front of the lens barrel to thethird frame 31.

A cylindrical outer peripheral surface of a supported part 31g providedon the main-guide shaft 32 for the third frame 31 is provided with astepped portion 31 c, and a cam portion 31 e disposed inside the steppedportion 31 c and formed from an inclined surface, as shown in FIG. 14A.

From this state, when a third frame drive motor 52 is rotated clockwiseas viewed from the front of the lens barrel, the third group lead screw34 is rotated clockwise through a gear mechanism including gears 71 to74, and the third frame female screw member 35 moves toward the subjectalong the optical axis X. At this time, the third frame 31 is rotatedclockwise by a moment force of the compression torsion spring 37, thecam portion 31 e engages with a first abutting portion 35 a provided onthe third frame female screw member 35.

Thereafter, when the third frame female screw member 35 is moved in theclosest position to the subject, the light-shielding strip 31 b of thethird frame 31 is moved to a position out of a third framephoto-interrupter 38 as a device for detecting a position of the thirdlens group 13, thereby the third frame photo-interrupter 38 generates areference signal in a range from L or a low level to H or a high level.Accordingly, a position of the third lens group 13 is controlled bypulse count based on the reference signal from the third framephoto-interrupter 38.

From this state, when the third frame female screw member 35 is moved toa retract-initiating position B of the third frame 31, as shown in FIG.14A, the third frame 31 further rotates clockwise, the stopper 31 acomes into abutment with the third frame sub-guide shaft 33 as shown inFIGS. 8 and 16A, as a result, a position of the third frame 31 on theoptical axis is determined. Consequently, approach operation of thethird lens group 13 to the optical axis is completed. In theretract-initiating position B, the third frame 31 is movable toward theretracted position S.

Meanwhile, the light-shielding strip 31 b shields the third framephoto-interrupter 38 shown in FIG. 16 A so that it is possible toconfirm that the third frame 31 is in the retract-initiating position B.When the third frame female screw member 35 is moved to theretract-initiating position B shown in FIG. 14A, the first abuttingportion 35 a of the third frame female screw member 35 contacts with afront engaging portion 31d of the stepped portion 31 c of the thirdframe 31. Again, the stepped portion 31 c of the third frame 31 has thecam portion 31 e and the front engaging portion 31 d which forms aplanner surface generally perpendicular to the third group main guideshaft 32.

The third frame 31 is constantly biased to move to a directiontransverse to the optical axis, that is to say, from the retractedposition to the optical axis and a direction along the optical axis,that is to say, from the subject to a retainer plate 81 beside the imageplane by the compression torsion spring 37 provided on the third groupmain-guide shaft 32.

In addition, a portion of the fixed frame 21 to which the compressiontorsion spring 37 contacts includes a step 37 a which is formed as aconcave portion for inserting one end of the compression torsion spring37, as shown in FIG. 14B, to prevent the compression torsion spring fromdeviating out of a center of the third group min-guide shaft 32considerably.

Next, when the third frame female screw member 35 is moved to a shortfocal length/wide angle position such as a wide angle position W shownin FIG. 14A, because the first abutting portion 35 a of the third framefemale screw member 35 presses the front engaging portion 31 d, thethird frame 31 is movable to the wide angle position along the opticalaxis X toward the subject.

Moreover, while the third frame female screw member 35 is disposedbetween the retract-initiating position B and a telephoto position T, asshown in FIG. 14, because the third frame 31 is constantly pressed alongthe optical axis toward the image plane by the compression torsionspring 37, all spaces generated among the third group lead screw 34, thethird frame female screw member 35 and the retainer plate 81 aredirected to the image plane, the third frame 31 can secure a positionalaccuracy in the direction of the optical axis.

The third frame female screw member 35 is screwed on the third grouplead screw 34 disposed substantially in parallel with the optical axis.The third frame female screw member 35 includes a rotation-preventingprojection 35 b in addition to the first abutting portion 35 a, whichengages with the above-described front engaging portion 31 d or the camportion 31 c of the third frame 31.

The rotation-preventing projection 35 b is fitted slidably into a guidegroove formed on the cylindrical part of the fixed frame 21 in parallelwith the optical axis as a rotation-preventing device for preventing thethird frame female screw member 35 from rotating along with the rotationof the third lead screw 34. In other words, the third frame female screwmember 35 is moved in the back and forth direction along the opticalaxis by the rotation of the third lead screw 34, because the third framefemale screw member 35 is prevented from rotating by therotation-preventing projection 35 b fitting into the guide groove of thefixed frame 21.

As shown in FIG. 14A in detail, when the third frame female screw member35 is moved further toward the image plane (left side in the drawing)from the retract-initiating position B shown in FIG. 14A, the thirdframe female screw member 35 engages with the cam portion 31 e of thestepped portion 31 c the third lend group-retaining frame 31.

The third frame 31 comes into contact with the retainer plate 81 by abiasing force of the compression torsion spring 37 clockwise, the thirdframe 31 is rotated counterclockwise against the clockwise biasing forceexerted by the compression torsion spring 37, therefore the third frame31 can be retracted.

On the other hand, while the third frame female screw member 35 is movedfrom the telephoto position T through the wide angle position W to theretract-initiating position B by the reverse rotation orcounterclockwise rotation of the third group lead screw 34, because thefirst abutting portion 35 a of the third frame female screw member 35engages with the front engaging portion 31 d of the stepped portion 31 cof the third frame 31, the third frame 31 moves gradually to direct fromthe subject to the image plane while maintaining a position on theoptical axis limited by the third frame sub-guide shaft 33 by thebiasing force toward the optical axis and the biasing force toward theimage plane.

Meanwhile, when the third frame female screw member 35 reaches theretract-initiating position B, a base end surface 31f abuts with theretainer plate 81, the third frame female screw member 35 is disposedwith an interval from the front engaging portion 31 d and contacts withthe cam portion 31 e of the stepped portion 31 c.

While the third frame female screw member 35 moves from theretract-initiating position B to the collapsed position S, the secondabutting portion 35 c of the third frame female screw member 35 comesinto sliding contact with the cam portion 31 e of the stepped portion 31c of the third frame 31 and rotates the third frame 31 against therotational biasing force exerted by the compression torsion spring 37,whereby the third frame 31 moves from the position on the optical axisto the collapsed position S. The collapsed position S of the third frame31 corresponds to a position at which it is moved toward the image planeby a predetermined pulse count number after the generation of thereference signal of the range from the H to the L generated from thethird frame photo-interrupter 38. After the third frame 31 is moved tothe collapsed position S, the first lens group 11, the second lens group12, and the shutter/aperture unit 15 are moved to the collapsible orcollapsed position.

In this example, before the third frame 31 is moved to the collapsedposition S, a fourth frame 41 (lens retaining frame) for retaining thefourth lens group 14 is first moved to the collapsed position. A firstcollapsed position of the fourth frame 41 corresponds to a position atwhich it is moved toward the image plane by a predetermined pulse countnumber after the generation of a storage reference signal of a rangefrom the H to the L generated by a fourth group reference detector orfourth group photo-interrupter 47. After the fourth frame 41 reaches thefirst collapsed position, the stored operation of the third frame 31 isinitiated.

That is to say, the third frame female screw member 35 moves toward theimage plane by a predetermined pulse count number from the generation ofthe stored reference signal from the H to the L by the third framephoto-interrupter 38 (see FIG. 16A) and the stored operation of thethird frame 31 is completed. After the completion of the storedoperation of the third frame 31, the first rotary cylinder 22 andstructural parts disposed inside the first rotary cylinder 22 and thefirst liner 23 and so on are stored before contacting with the thirdframe 31. This results in the storage of the first rotary cylinder 22and so on without interfering with the third frame 31.

Positions of the first rotary cylinder 22 and so on can be set by adrive pulse count generated by a zoom count detector comprising a piniongear attached directly to an output shaft of the zooming motor 51 andhaving an encoder structure and for example, a first and second framesphoto-interrupter 51 a disposed adjacent the pinion gear, for example.

Meanwhile, although the DC motor is used as the drive source for movingthe first rotary cylinder 22 and the drive position of the first rotarycylinder 22 is detected by the detector comprising the encoder and thephoto-interrupter, in the above-mentioned example, the similar functioncan be accomplished by substituting a pulse motor structure for thewhole of the above-mentioned structure.

To prevent the third frame 31 from collision with the other parts, animpact-preventing member 36 is, as shown in particular in FIGS. 2 and 7,rotatably supported on the fixed frame 21 in the vicinity of the thirdgroup main-guide shaft 32 and includes a rotated portion provided at oneend of the impact-preventing member and an engaging projection 36 a. Theimpact-preventing member 36 is constantly biased to cause the engagingprojection 36a to move toward the optical axis X by a spring or thelike.

When the third frame 31 is positioned in the collapsed position, theimpact-preventing member 36 is pushed out by a rotating force of thethird frame 31 against a biasing force of the spring, and is deviatedoutside the third frame 31 (see FIG. 2 and FIG. 7, specifically).

When the third frame 31 is rotated and positioned on the optical axis,the impact-preventing member 36 is released from engagement with thethird frame 31, and is rotated to cause the engaging projection 36a tobe projected toward the optical axis X by the biasing force, therebycausing the engaging projection 36a to project from the inner surface ofthe fixed frame of the fixed frame 21. At this time, in addition to thefirst rotary cylinder 22 and the first liner 23, the second rotarycylinder 24, the second liner 25, the cam cylinder 26 and thelineally-moving cylinder 27 are all positioned on the subject side withrespect to the projected position of the engaging projection 36 a.Therefore, the engaging projection 36 a is positioned to projectinwardly of an outer peripheral edge of the base portion of each of thefirst rotary cylinder 22 and the first liner 23 (see FIG. 5, FIG. 6, andFIG. 8, specifically).

With such a structure, even if an operator rotates the first rotarycylinder 22 manually forcibly and moves it to the collapsed position,the impact-preventing member 36 first contacts with the first rotarycylinder 22. Therefore, because the base portion of the first rotarycylinder 22 cannot be moved toward the image plane than the position ofthe impact-preventing member 36 along the optical axis, the first rotarycylinder 22 is prevented from contacting with the third frame 31.Accordingly, it is possible to accomplish the prevention of breaking,damage or the like of the third frame 31 due to a strength externalforce.

In addition, the first rotary cylinder 22 can be first moved to thecollapsed position after the third frame 31 is moved to the collapsedposition correctly. Therefore, in a used or photographing state of thelens barrel, in which the movable cylinders such as the first rotarycylinder 22 and so on are extended, when a great pressure is exerted ona leading end of the lens barrel and so on by a drop of the lens barrelor the like, the engaging projection 36 a of the impact-preventingmember 36 engages with the first rotary cylinder 22 and the first liner23, and hence further retraction of the first rotary cylinder 22 and thefirst liner 23 (as well as the second rotary cylinder 24, the secondliner 25, the cam cylinder 26, and the lineally-moving cylinder 27)toward the third lens group 13 is prevented, so that the third frame 31and the third lens group 13 are prevented from being damaged.

The third group lead screw 34 is rotated in forward and reversedirections by a third frame drive motor 52. The rotation of the thirdframe drive motor 52 is transmitted to the third group lead screw 34 viagears 71, 72, 73, and 74 arranged in sequence.

Next, a drive structure of the fourth lens group 14 is explained withreference to FIGS. 7, 8, 20A and 20B.

The fourth lens group 14 used as a focusing lens for focusing the lensgroups in the illustrated embodiment is retained by the fourth frame 41,as shown in FIGS. 20A and 20B. The fourth frame 41 includes a sleeveportion 41 a in which the fourth frame main-guide shaft 44 disposed inparallel with the optical axis and fixed to a lens barrel base 82 isfitted, and a rotation-preventing portion 41 b in which the fourth framesub-guide shaft 42 disposed in parallel with the optical axis and fixedto the lens barrel base 82 is fitted, to limit the rotation of thefourth frame 41. With such a structure, the fourth frame 41 can be movedfreely along the fourth frame main-guide shaft 44 or the optical axis. Afourth frame drive motor 53 comprising a stepping motor is used as adrive source for driving the fourth frame 41 in the illustratedembodiment. Provided on an output shaft of the fourth frame drive motor53 is a fourth frame lead screw 45 which is threaded into a threadedhole provided in a fourth frame female screw member 46.

The fourth frame 41 has an opening for inserting the fourth frame femalescrew member 46. The opening has an engaging portion 41c for engagingwith the fourth frame female screw member 46 in a perpendicular plane tothe optical axis in a side of the image plane. The fourth frame 41 isalways engaged with the fourth frame female screw member 46 by allowingthe fourth frame 41 to bias to the subject by a fourth frame spring 43.

The fourth frame female screw member 46 has a radially projectedprotrusion 46 a. The protrusion 46 a is engaged in a bore 41 d providedin one side of the opening for inserting the fourth frame female screwmember 46 of the fourth frame 41 so that the rotation of the fourthframe female screw member 46 is stopped.

In this way, when the fourth frame drive motor 53 which is the steppingmotor is driven, the fourth frame lead screw 45 rotates, the fourthframe female screw member 46 is moved in the forward and reversedirections along an axis of the fourth frame lead screw 45 or theoptical axis X. Because the fourth frame 41 engages with the fourthframe female screw member 46, the fourth frame 41 is moved along theoptical axis following to the movement of the fourth frame female screwmember 46. In this case, although the fourth frame lead screw 45 isformed on the output shaft of the fourth frame drive motor 53, thefourth frame lead screw 45 may be rotated by constituting the fourthframe drive motor 53 and the fourth frame lead screw 45 separately andconnecting them through gears or the like.

The fourth frame 41 is provided with a light-shielding piece 41 e whichshields an optical passage of a fourth group photo-interrupter 47provided on the lens barrel base 82, the light-shielding piece 41 e iscapable of light-shielding or passing light through the optical passageof the fourth group photo-interrupter 47 in response to the movement ofthe fourth frame 41. In this case, the fourth frame 41 can be moved in apredetermined position by recognizing as a reference position a time atwhich the light-shielding pieces is set from the light-shielding stateto the light-passing state, energizing a pulse waveform of any pulsenumber from the reference position, rotating the fourth frame drivemotor 53.

Meanwhile, the fourth frame 41 has a concave portion 41 f which isprovided in an outer peripheral edge thereof and allows thelight-shielding strip 31 b of the third frame 31 as thephoto-interrupter to move toward the optical axis to avoid theinterference with the fourth frame 41, thereby the moved amount of thefourth frame 41 can be increased and a range capable of focusing can beenlarged. Moreover, as described above, there is a clearance between thefourth frame 41 and the fourth frame female screw member 46 in thedirection of the optical axis, but the position in the direction of theoptical axis of the fourth frame 41 can be controlled accurately byconstantly biasing the fourth frame 41 toward the subject by the fourthframe spring 43.

The collapsed position of the first rotary cylinder 22, the first liner23, the first lens group 11, the second lens group 12, and theshutter/aperture unit 15 is controlled based on the zoomposition-reference signal generated by the zoom position detectorcomprising the photo-reflector and so on disposed in the fixed frame 21.That is to say, it is possible to complete the storing operation bymoving them toward the image plane by the predetermined pulse countnumber of the drive pulse generated by the pinion gear acting as theencoder and the zoom count detector disposed adjacent to the pinion gearafter the change of from the H to the L of the zoom position storagereference signal occurs.

In storing, the fourth frame 41 is positioned in the first collapsedposition as described above, while, when the first rotary cylinder 22 ismoved to the collapsed position, the most distal surface of the firstrotary cylinder 22 or the first liner 23 contacts with the fourth frame41 and presses the fourth frame 41 to move to the second collapsedposition finally.

By such an operation, even if variations of the attached position of thefourth group photo-interrupter 47 in the direction of the optical axisoccur, the fourth frame 41 can be moved to the collapsed positionaccurately without requiring a complicated adjustment. Such an operationcan be accomplished for the reason that a length of the engaging spaceformed in the fourth frame 41, in the direction of the optical axis islarger than a thickness of the fourth frame female screw member 46.

The zooming motor 51 for moving the first lens group 11, the second lensgroup 12, and the shutter/aperture unit 15 is structured by the DC motoras described above in the illustrated embodiment, the third frame drivemotor 52 for driving the third lens group 13 and the fourth frame drivemotor 53 for driving the fourth lens group 14 are generally configuredto use a pulse motor, for example, are driven in conjunction with eachother in a software-like manner to achieve an appropriate zooming actionperformed mainly by the first to the third lens groups 11-13 and anappropriate focusing action performed mainly by the fourth lens group14, for example.

Here, a drive control system for the lens groups constituting the lensbarrel is described in detail.

The drive control system is shown in FIG. 21. The drive control systemincludes a central processing unit (CPU) 501, a motor driver 502, afirst and second frames DC motor 503, a first aperture stop motor 504, asecond aperture stop motor 505, a shutter motor 506, a third frame pulsemotor 507, a fourth frame pulse motor 508, a first and second framesphoto-interrupter 509, a first and second frames photo-reflector 510, athird frame photo-interrupter 511, a fourth frame photo-interrupter 512,a first and second frames photo-interrupter drive circuit 513, a firstand second frames photo-reflector drive circuit 514, a third framephoto-interrupter drive circuit 515, and a fourth framephoto-interrupter drive circuit 516.

The CPU gives a command such as an initial setting of the motor driver502, the selection for a drive motor, the setting of a drive voltage, adirection for driving and so on to the motor driver 502. The motordriver 502 controls the motor system of the first and second frames DCmotor 503, the first aperture stop motor 504, the second aperture stopmotor 505, the shutter motor 506, the third frame pulse motor 507, thefourth frame pulse motor 508 and so on, in accordance with the commandfrom the CPU 501.

The first and second frames DC motor 503 drives the first and secondlens groups 11 and 12. As always, the first and second groups 11 and 12are driven separately with respect to each other through a cam mechanismin response to the drive of the first and second frames DC motor 503.The first aperture stop motor 504 and the second aperture stop motor 505are configured to drive an aperture stop of the shutter/aperture unit15. The shutter motor 506 drives a shutter of the shutter/aperture unit15. The third frame pulse motor 507 drives the third lens group 13. Thefourth frame pulse motor 508 drives the fourth lens group 14.

The CPU 501 supplies a drive electricity to the first and second framesphoto-interrupter 509, the first and second frames photo-reflector 510,the third frame photo-interrupter 511, and the fourth framephoto-interrupter 512 as a position-detecting device through the firstand second frames photo-interrupter drive circuit 513, the first andsecond frames photo-reflector drive circuit 514, the third framephoto-interrupter drive circuit 515, and the fourth framephoto-interrupter drive circuit 516. The CPU 501 also acquires apositional information signal detected by the first and second framesphoto-interrupter 509, the first and second frames photo-reflector 510,the third frame photo-interrupter 511, and the fourth framephoto-interrupter 512.

The first and second frames photo-interrupter drive circuit 513, thefirst and second frames photo-reflector drive circuit 514, the thirdframe photo-interrupter drive circuit 515, and the fourth framephoto-interrupter drive circuit 516 have a function to control suitablya level of a projecting current and an output signal of each of thefirst and second frames photo-interrupter 509, the first and secondframes photo-reflector 510, the third frame photo-interrupter 511, andthe fourth frame photo-interrupter 512.

The motor driver 502 receives a command from the CPU 501 and executesthe command. The CPU sets a designated voltage to one or more selectedmotors of the first and second frames DC motor 503, the first aperturestop motor 504, the second aperture stop motor 505, the shutter motor506, the third frame pulse motor 507, the fourth frame pulse motor 508,and controls them in accordance with a timing of drive command.

Here, a lens barrier 62 for protecting the lens barrel is described asfollows.

The lens barrier 62 shown in FIG. 3 to FIG. 5 is disposed to cover aside of the first lens group 11 facing the subject, in the stored state,and protects the lens group from contaminations or damages. The lensbarrier 62 is moved in back and forth directions transverse to theoptical axis by a barrier drive system 63. FIGS. 3 and 4 show a state inwhich the lens barrier 62 is closed, and FIG. 5 shows a state in whichthe lens barrier 62 is almost opened. The barrier drive system 63 drivesthe lens barrier 62 between the closed position (FIGS. 3 and 4) and theopened position (a position farther from the optical axis than theposition shown in FIG. 5) through the operation of a barrier-operatingelement (see a barrier-operating element 301 in FIG. 17 A). The barrierdrive system 63 has a function to bias the lens barrier 62 in a closingdirection at the closed position and in an opening direction at theopened position.

Therefore, when driving the lens barrier 62 in the closed state towardthe opening direction, the lens barrier 62 is moved to the opened statesemi-automatically when the lens barrier 62 passes a predeterminedposition. Also, when an attempt is made to close the lens barrier 62from the opened state, the lens barrier 62 is moved to the closed statesemi-automatically when the lens barrier 62 passes a predeterminedposition. The position in the closed state is not necessarily requiredto be the same as the predetermined position in the opened state,rather, it is preferable that the lens barrier has a certain degree ofhysteresis characteristics in the movement to accomplish a smoothoperation of the lens barrier 62.

A barrier control strip 61 is provided on a side of the fixed frame 21in the direction of opening the lens barrier 62 so as to be capable ofsliding in a direction along the optical axis, and is biased toward thesubject by a spring or the like as needed. In the stored state, anengaging portion of the barrier control strip 61 which is formed into abent shape engages with base edge surfaces of the first rotary cylinder22 and the first liner 23 and is biased toward the image surface againsta biasing force of the spring, and hence is not in contact with the lensbarrier 62. In the used or photographing state, the lens barrier 62 iscompletely away from the respective lens groups and retaining framesthereof. In this state, engagement of the engaging portion of thebarrier control strip 61 is released, and hence the barrier controlstrip 61 is biased toward the subject by the biasing force, and then, abarrier-intercepting portion at the distal end enters into a passage ofthe lens barrier 62.

In this state, when the lens barrier 62 is rapidly operated to move thelens barrel to the collapsed position, there is a possibility that thelens barrier 62 hits against the lens barrel. However, since thebarrier-intercepting portion at the distal end of the barrier controlstrip 61 crosses the passage of the lens barrier 62 to prevent the lensbarrier 62 from entering into a moving passage of the lens barrel. Whenthe respective lens groups are stored and the stored state is completed,the base edge surfaces of the first rotary cylinder 22 and the firstliner 23 engage with the engaging portion of the barrier control strip61, which is formed into the bent shape, to energize the engagingportion toward the image surface against the biasing force. Therefore,the lens barrier 62 can be moved to the front portion of the lensbarrel, and hence the lens barrier 62 is correctly set to the closedposition. In this manner, the interference between the lens barrier 62and the lens cylinders retaining the lens groups can be effectivelyprevented.

<Actuation Sequence>

An actuation sequence of the above-mentioned drive control system isexplained with reference to FIG. 22.

By opening the lens barrier 62, a barrier switch signal from a barrierswitch (not shown) changes from the H to the L and an initial setting ofthe lens barrel is initiated. Meanwhile, the barrier switch is operatedby opening mechanically the lens barrier 62 with an operating lever orthe like (not shown), while the lens barrier may be opened by operationof the barrier switch. Executing the initial setting causes theinitialization of the motor driver 502 for driving the motor system, andthe initialization of the first and second frames photo-interrupter 509,the first and second frames photo-reflector 510, the third framephoto-interrupter 511, and the fourth frame photo-interrupter 512, asthe position detecting device for a position through the first andsecond frames photo-interrupter drive circuit 513, the first and secondframes photo-reflector drive circuit 514, the third framephoto-interrupter drive circuit 515, and the fourth framephoto-interrupter drive circuit 516.

In the case that detected results by the first and second framesphoto-interrupter 509, the third frame photo-interrupter 511, and thefourth frame photo-interrupter 512 indicate the collapsed position, thefirst and second frames DC motor 503 is adapted to drive to the wideangle position. A driven amount of the first and second frames DC motor503 is detected by the first and second frames photo-interrupter 509 fordetecting the moving amount of the first and second lens groups. Themoving amount is detected by counting edge portions of the pulse signal(PI signal) by the first and second frames photo-interrupter 509.

A period for actuating right after the first and second frames DC motor503 is actuated is set, during which, the drive voltage is lower than aconstant voltage in order to prevent an incoming current by the DCmotor. After the actuation period is completed, the drive voltage isincreased to a stationary voltage.

A period for monitoring the barrier switch or barrier SW right after theinitiation of the actuation of the first and second frames DC motor 503is set and a state of the barrier switch signal is monitored by the CPU501. During monitoring period, if the barrier switch signal indicatesthe opening state of the lens barrier, the shutter is set in the fullopening by the shutter motor 50 for driving the shutter. Then, theaperture stop is set in an intermediately restricted state by the firstand second aperture stop motors 504 and 505.

In this example, although the aperture stop is set in the intermediatelyrestricted state, it may be set in an opened state or fully openedstate.

Next, the fourth lens group 14 is previously driven through the fourthpulse motor 508. By achieving the previous drive of the fourth lensgroup 14, the total time from the initiation of the drive of the firstand second lens groups to the completion of the drive of the finalfourth lens group 14 can be reduced. Moreover, it is possible to greatena torque when driving and prevent the interference of the fourth lensgroup with the other parts by setting a pulse rate of the fourth framepulse motor 508 in the previous drive thereof lately than that in thenormal driving state.

Meanwhile, the driven amount of the fourth lens group by the fourthframe pulse motor 508 is set so that the third and fourth lens groupsinterfere with respect to each other.

When the previous drive of the fourth lens group 14 is completed, thewaiting for detecting reference position by the first and second framesphoto-reflector 510 is set. A place where the reference position signalchanges from the H to the L becomes the reference position or HPposition of the first and second lens groups 11 and 12. When thereference position or HP position of the first and second lens groups 11and 12 is detected, positional information of the first and second lensgroups 11 and 12 is reset. The movement of the first and second lensgroups is controlled by counting the pulse-like signal (PI signal) bythe first and second frames photo-interrupter 509 based on thepositional information to acquire the moved amount of the first andsecond lens groups until the wide angle position. The wide angleposition is previously set, but it can be changed by storing it in anonvolatile memory and rewriting it.

A specified pulse period before reaching the wide angle position is astop controlling period, overrun in reaching the wide angle position canbe reduced by lowering the drive voltage in accordance with residualpulse numbers to the wide angle position. If the first and second lensgroups reach the wide angle position by counting the PI signal by thefirst and second frames photo-interrupter 509, a braking control is madein order to stop the first and second lens groups. An amount of overrunduring the braking period is counted so that the final position of thefirst and second lens groups 11 and 12 is decided.

Moreover, when the reference position or HP position of the first andsecond lens groups 11 and 12 is detected, the drive of the third framepulse motor 507 in the direction of wide angle position is initiated tocontrol the third lens group 13 with the first and second lens groups 11and 12. The driving time of the third lens group 13 can be reduced bysetting the pulse rate in driving the third group pulse motor highly orrapidly than that in the normal drive.

The third lens group 13 is waited for detecting the reference positionby the third frame photo-interrupter 511. A place where the referenceposition signal or HP signal by the third frame photo-interrupter 511changes from the L to the H becomes the reference position or HPposition of the third lens group 13. When the reference position or HPposition is detected, positional information of the third lens group 13is reset. The third lens group 13 is pulse-driven by the third framepulse motor 507 based on the positional information to obtain the movedamount of the third lens group 13 to the wide angle position. The wideangle position is previously set, but it can be changed by storing it ina nonvolatile memory such as an EEPROM or the like and rewriting it.

In addition, the final stopping position of the third lens group 13becomes a position in consideration of overrun of the first and secondlens groups 11 and 12. That is to say, because the stopping position ofthe first and second lens groups 11 and 12 is the wide angle positionplus overrun amount, the stopping position of the third lens group 13 isalso the wide angle position plus a in consideration of overrun of thefirst and second lens groups 11 and 12. A value of the α is obtained bya linear calculation depending on pulse numbers between the zoomingpositions of the first and second lens groups 11 and 12, the overrunamount and a pulse number between the zooming positions of the thirdlens group 13. The zooming position is one of sections divided into 16equally between the wide angle position and the telephoto position(between W and T).

If the drive of the first and second lens groups 11 and 12 is completed,the reference position or HP position of the third lens group 13 isdetected, and the third lens group 13 is driven more than the specifiedpulse number, the drive of the fourth frame pulse motor 508 in thedirection of a wide angle infinite position is initiated. If the driveof the first and second lens groups 11 and 12 is not completed, or thethird lens group 13 is not driven more than the specified pulse from thereference position, the drive of the first and second lens groups 11 and12 is completed, and a standby state is set until the third lens group13 is driven more than the specified pulse from the reference position.When the drive of the first and second lens groups 11 and 12 are notcompleted and the fourth frame pulse motor 508 is driven, the threemotors are driven simultaneously to increase current consumption.Therefore, in the example, only the third and fourth lens groups aredriven simultaneously. Moreover, when the fourth lens group 14 is drivenbefore the third lens group 13 reaches the position more than thespecified pulse number, the interference between the third and fourthlens groups 13 and 14 occurs. Therefore, the drive of the fourth lensgroup 14 is initiated after the third lens group 13 is driven more thanthe specified pulse number.

The fourth lens group 14 is waited for detecting the reference positionby the fourth frame photo-interrupter 512. In addition, currentconsumption can be reduced by setting the drive voltage of the fourthframe pulse motor 508 to be lower than that of the normal drive. A placewhere the reference position signal or HP signal by the fourth framephoto-interrupter 512 changes from the L to the H becomes the referenceposition or HP position of the fourth lens group 14. When the referenceposition or HP position of the fourth lens group is detected, positionalinformation of the fourth lens group 14 is reset. The fourth lens group14 is pulse-driven by the fourth frame pulse motor 508 based on thepositional information to obtain the moved amount of the fourth lensgroup 14 to the wide angle position. The wide angle position ispreviously set, but it can be changed by storing it in a nonvolatilememory such as an EEPROM or the like and rewriting it.

In the embodiment, as described above and shown in a timing chart ofFIG. 22, the current consumption can be reduced by limiting thesimultaneously driven motors to two motors, and a time of actuating themotors can be shortened by the optimum drive of the motors.

Next, a case in which the barrier switch signal is changed in a closedstate during a period for monitoring the barrier switch right after theactuation of the first and second frames DC motor 503 is initiated isexplained with reference to FIG. 23. If the barrier switch signal ischanged from the opened state to the closed state during the period, thedrive of the first and second frames DC motor 503 is stopped.

Thereafter, the drive of the first and second frames DC motor 503 isinitiated by a moved amount in the direction of the collapsed positionor the specified pulse number. In this case, the drive voltage is lowerand breaking and damage are prevented from generating even if operatingparts of the lens barrier impact with switch first and second lensgroups and so on in the end of a collapsed position. By such a control,the first and second lens groups are prevented from interfering with thelens barrier.

[Reset Sequence]

Moreover, if the detected result of the first and second photo-reflector510 is not the collapsed position (reference position HP, signal L), thedetected result of the third frame photo-interrupter 511 is not thecollapsed position (reference position HP, signal H), or the detectedresult of the fourth frame photo-interrupter 512 is not the collapsedposition (reference position HP, signal H), the reset sequence drive isexecuted.

The reset sequence is described referring to FIG. 24 as follows. <Withrespect to first and second group HP signal=H, third group HP signal=L,fourth group HP signal=L>First, as the reset operation of the first andsecond lens groups 11 and 12, the reference position or HP position ofthe first and second lens groups is detected, and the first and secondlens groups are moved to the wide angle position (first and secondgroups: Reset). Next, as the storing operation of the fourth lens group14, the reference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the collapsed position(fourth group: storage).

Subsequently, as the reset operation of the third lens group 13, thereference position or HP position of the third lens group 13 isdetected, and the third lens group is moved to the wide angle position(third group: Reset).

Finally, as the reset operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the wide angularinfinite position (fourth group: Reset). <With respect to first andsecond group HP signal=H, third group HP signal=L, fourth group HPsignal=H>First, as the retiring operation of the first and second lensgroups 11 and 12, the first and second lens groups are driven in thedirection of the telephoto and pulse-driven by the specified pulse afterthe lowering of the reference signal is detected (first and groups;retire). Next, as the storing operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the collapsed position(fourth group: storage). Subsequently, as the reset operation of thefirst and second lens groups 11 and 12, the reference position or HPposition of the first and second lens groups 11 and 12 is detected, andthe first and second lens groups are moved to the wide angle position(first and second groups: Reset).

Next, as the reset operation of the third lens group 13, the referenceposition or HP position of the third lens group 13 is detected, and thethird lens group is moved to the wide angle position (third group:Reset). Finally, as the reset operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the wide angularinfinite position (fourth group: Reset). <With respect to first andsecond group HP signal=H, third group HP signal=H, fourth group HPsignal=L, first and second group HP signal=H, third group HP signal=H,fourth group HP signal=H >First, as the retiring operation of the firstand second lens groups 11 and 12, the first and second lens groups aredriven in the direction of the telephoto and pulse-driven by thespecified pulse after the lowering of the reference signal is detected(first and groups; retire). Next, as the storing operation of the fourthlens group 14, the reference position or HP position of the fourth lensgroup 14 is detected, and the fourth lens group is moved to thecollapsed position (fourth group: storage). If the reference position orHP position of the fourth lens group 14 can be detected, as the storingoperation of the third lens group, the reference position or HP positionof the third lens group 13 is detected, and the third lens group ismoved to the collapsed position (third group: storage). If the referenceposition or HP position of the fourth lens group 14 cannot be detected,because it is considered that the fourth lens group is interfered withthe third lens group 13, the storing operation of the third lens group13 is previously carried out (third group: storage).

If the storing operation of the third lens group 13 is completed, andthen the storing operation of the fourth lens group 14 is carried out(fourth group: storage). If the HP position is not detected at the timeof operating the storage of the third lens group 13, because it isconsidered that the third lens group 13 is interfered with the fourthlens group 14, as the retiring operation of the third lens group 13, thethird lens group 13 is driven by the specified pulse count in thedirection of the telephoto (third group: retire). Thereafter, thestoring operation (fourth group: storage) of the fourth lens group 14and the storing operation (third group: storage) of the third lens group13 are carried out.

Subsequently, as the reset operation of the first and second lens groups11 and 12, the reference position or HP position of the first and secondlens groups 11 and 12 is detected, and the first and second lens groupsare moved to the wide angle position (first and second groups: Reset).Next, as the reset operation of the third lens group 13, the referenceposition or HP position of the third lens group 13 is detected, and thethird lens group is moved to the wide angle position (third group:Reset). Finally, as the reset operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the wide angularinfinite position (fourth group: Reset). <With respect to first andsecond group HP signal=L, third group HP signal=L, fourth group HPsignal=L, first and second group HP signal=L, third group HP signal=L,fourth group HP signal=H>.

First, as the storing operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the collapsed position(fourth group: storage). Next, as the storing operation of the thirdlens group 13, the reference position or HP position of the third lensgroup 13 is detected, and the third lens group is moved to the collapsedposition (third group: storage). Next, as the reset operation of thefirst and second lens groups 11 and 12, the reference position or HPposition of the first and second lens groups is detected, and the firstand second lens groups are moved to the wide angle position (first andsecond groups: Reset). Subsequently, as the reset operation of the thirdlens group 13, the reference position or HP position of the third lensgroup 13 is detected, and the third lens group is moved to the wideangle position (third group: Reset). Finally, as the reset operation ofthe fourth lens group 14, the reference position or HP position of thefourth lens group 14 is detected, and the fourth lens group is moved tothe wide angular infinite position (fourth group: Reset).

<With respect to first and second group HP signal=L, third group HPsignal=H, fourth group HP signal=L, first and second group HP signal=L,third group HP signal=H, fourth group HP signal=H>

First, as the storing operation of the fourth lens group 14, thereference position or HP position of the fourth lens group 14 isdetected, and the fourth lens group is moved to the collapsed position(fourth group: storage). If the reference position or HP position of thefourth lens group 14 can be detected, as the storing operation of thethird lens group 13, the reference position or HP position of the thirdlens group 13 is detected, and the third lens group is moved to thecollapsed position (third group: storage).

If the reference position or HP position of the fourth lens group 14cannot be detected, because it is considered that the fourth lens groupis interfered with the third lens group 13, the storing operation of thethird lens group 13 is previously carried out (third group: storage). Ifthe storing operation of the third lens group 13 is completed, and thenthe storing operation of the fourth lens group 14 is carried out (fourthgroup: storage). If the HP position is not detected at the time ofoperating the storage of the third lens group 13, because it isconsidered that the third lens group 13 is interfered with the fourthlens group 14, as the retiring operation of the third lens group 13, thethird lens group 13 is driven by the specified pulse count in thedirection of the telephoto (third group: retire).

Thereafter, the storing operation (fourth group: storage) of the fourthlens group 14 and the storing operation (third group: storage) of thethird lens group 13 are carried out. Subsequently, as the resetoperation of the first and second lens groups 11 and 12, the referenceposition or HP position of the first and second lens groups 11 and 12 isdetected, and the first and second lens groups are moved to the wideangle position (first and second groups: Reset). Next, as the resetoperation of the third lens group 13, the reference position or HPposition of the third lens group 13 is detected, and the third lensgroup is moved to the wide angle position (third group: Reset). Finally,as the reset operation of the fourth lens group 14, the referenceposition or HP signal of the fourth lens group 14 is detected, and thefourth lens group is moved to the wide angular infinite position (fourthgroup: Reset).

[Storing Sequence]

The barrier switch signal changes from L to H by closing the lensbarrier 62 to initiate the storing operation. Meanwhile, the barrierswitch may be operated by mechanically closing the lens barrier 62 bymeans of an operating lever or the like, or the lens barrier 62 may beclosed by operation of the barrier switch.

The shutter of the shutter/aperture stop unit 15 is set in the fullyclosed state through the full closing control of the shutter by theshutter motor 506. Next, the aperture stop of the shutter/aperture stopunit 15 is set in the intermediately restricted state through theintermediate restricting control of the aperture stop by the first andsecond aperture stop driving motors 504 and 505. Subsequently, thestoring drive of the fourth lens group 14 is achieved through the fourthframe pulse motor 508. The standby for detecting the reference positionof the fourth frame pulse motor 508 by the fourth framephoto-interrupter 512 is set after the drive of the fourth frame pulsemotor 508 to the collapsed position is initiated.

The fourth frame pulse motor 508 is pulse-driven by a moved amount tothe collapsed position from a place where the reference positionalsignal or HP signal by the fourth frame photo-interrupter 512 changesfrom H to L to the collapsed position. The moved amount to the collapsedposition is previously set, but the moved amount can be changed bystoring it in a nonvolatile memory such as an EEPROM or the like andrewriting it.

Next, the drive of storing the third lens group 13 is executed throughthe third frame pulse motor 507. The third lens group 13 is waited fordetecting the reference position by the third frame photo-interrupter511 by initiating the drive of the third frame pulse motor 507 in thedirection of the collapsed position.

The third lens group 13 is pulse-driven by the moved amount to thecollapsed position from the place where the reference position signal orHP signal by the third frame photo-interrupter 511 changes from H to Lto the collapsed position. Although the moved amount to the collapsedposition is set previously, the moved amount can be changed by storingit in a nonvolatile memory such as an EEPROM or the like and rewritingit.

The drive pulse rate of the third frame pulse motor 507 between thereference position and the collapsed position is lower than the drivepulse rate until the reference position. In this way, a smooth pulsedrive can be accomplished by changing the pulse rate in accordance withan area in which a torque is necessary.

Next, the drive of storing the first and second lens groups 11 and 12 isexecuted through the first and second frames DC motor 503. The first andsecond lens groups are waited for detecting the reference position bythe first and second frames photo-reflector 510 by initiating the driveof the first and second frames DC motor 503 in the direction of thecollapsed position.

The control for the moved amount of the first and second lens groups 11and 12 is achieved by counting the pulse-like signal or PI signal by thefirst and second frames photo-interrupter 509 to acquire the movedamount to the collapsed position from the place where the referenceposition signal or HP signal by the first and second framesphoto-reflector 510 changes from L to H to the collapsed position.Although the moved amount to the collapsed position is set previously,the moved amount can be configured to be changed by storing it in anonvolatile memory such as an EEPROM or the like and rewriting it.

In the drive for storing the first and second lens groups 11 and 12, ifthe first and second lens groups 11 and 12 reach the collapsed positionby counting the PI signal by the first and second framesphoto-interrupter 509 without dropping the voltage of the first andsecond frames DC motor 503 before stopping it, a breaking control isachieved in order to stop the drive of the first and second lens groups11 and 12. This is reason the first and second group DC motor is notstopped at the middle of drive due to the dropping of voltage.

[Changing Magnification Sequence]

A sequence for operating a changing magnification is described withreference to a flow chart shown in FIG. 26.

When a changing magnification process is initiated by operating a zoomlever, zoom button or the like, whether it is necessary to retire thefourth lens group 14 is determined (step S11). It is determined in thestep S11 that the retire process for the fourth lens group is requiredif the fourth lens group 14 is disposed in a nearer position than apredetermined position in the changing magnification process from thetelephoto to the wide angle. Next, a direction of drive of the changingmagnification is determined (step S12). If it is the changingmagnification from the wide angle to the telephoto, the drive of thefirst and second lens groups 11 and 12 is initiated by operating thefirst and second frames DC motor 503 (step S13).

Next, whether the first and second lens groups 11 and 12 are stopped isdetermined (step S14). It is determined in the step S 14 that the firstand second lens groups 11 and 12 are stopped in a case satisfying eitherone of conditions in which if a zoom driving switch operated by changingmagnification manipulation through the zoom lever or zoom button or thelike becomes off, if the first and second lens groups reach a positionin front of a predetermined amount from the telephoto position in thedrive from the wide angle to the telephoto, and if the first and secondlens groups reach a position in front of a predetermined amount from thewide angle position in the drive from the telephoto to the wide angle.

If the first and second lens groups 11 and 12 are stopped, whether thethird lens group 13 is driving is determined (step S15), if the thirdlens group 13 is stopping, the stopping operation of the first andsecond lens groups 11 and 12 is executed (step S16) and the breakingoperation of the first and second lens groups 11 and 12 is executed(step S17). Subsequently, the driving direction of the changingmagnification is determined (step S18), if it is the changingmagnification from the wide angle to the telephoto, drive for correctinga position of the third lens group 13 is achieved (step S19), the driveof the aperture stop is executed (step S20), and the process iscompleted and returned from the step S20 to a process waiting state.

In the step S11, if it is determined that the retire process of thefourth lens group 14 is required, the retire process of the fourth lensgroup 14 is executed (step S21), and the process is shifted from thestep S21 to the step S12. In the step S12, if it is determined thechanging magnification driving direction is the changing magnificationfrom the telephoto to the wide angle, the retire process of the thirdlens group 13 is executed (step S22), the process is shifted from thestep S22 to the step S14.

In the step S14, if it is determined that the first and second lensgroups 11 and 12 continue to drive without stopping them, whether thethird lens group 13 is driving is determined (step S23), if the thirdlens group 13 is stopping, whether the drive of the third lens group 13is initiated is determined (step S24).

It is determined in the step S 24 that the drive of the third lens group13 is permitted in a case satisfying one of conditions in which if thefirst and second lens groups 11 and 12 are driven more than thespecified driven amount after the initiation of the drive of the firstand second lens groups, if the position of the third lens group 13 isaway a predetermined amount or more from the position of the first andsecond lens groups 11 and 12 when the first and second lens groups passa predetermined zooming point in the driving state that the third lensgroup 13 is re-driven from the wide angle to the telephoto, and if theposition of the third lens group 13 is approaching a predeterminedamount or more to the position of the first and second lens groups 11and 12 when the first and second lens groups pass a predeterminedzooming point in the driving state that the third lens group 13 isre-driven from the telephoto to the wide angle.

In the step S24, if the drive of the third lens group 13 is permitted,the drive of the third lens group is initiated (step S25), the processis returned from the step S25 to the step S14. In the step S24, if thedrive of the third lens group 13 is not permitted, the process isreturned from the step S24 to the step S 14 directly.

In the step S23, if it is determined that the third lens group 13 isdriving, whether the drive of the third lens group 13 is stopped isdetermined (step S26). It is determined in the step S26 that the thirdlens group 13 is permitted in a case satisfying one of conditions inwhich if the position of the third lens group 13 approaches apredetermined amount or more to the position of the first and secondlens groups 11 and 12 in the drive from the wide angle to the telephoto,and if the position of the third lens group 13 is away a predeterminedor more from the position of the first and second lens groups 11 and 12in the drive from the telephoto to the wide angle.

In the step S26, if the stop of the third lens group 13 is permitted,the stop of the third lens group is initiated (step S27), the process isreturned from the step S27 to the step S14. In the step S26, if the stopof the third lens group 13 is not permitted, the process is returned thestep S26 to the step S14 directly.

In the step S15, if it is determined that the third lens group 13 isdriving, the stop of the third lens group 13 is initiated (step S28),the process is shifted from the step S28 to the step S16. In the stepS18, if it is determined that the changing magnification drivingdirection is the changing magnification from the telephoto to the wideangle, a backlash operation is executed (step S29), the process isshifted from the step S29 to the step S19.

Next, a changing magnification operation depending on the flow chart isexplained every the direction of changing magnification in detail.

[From Wide Angle to Telephoto]

First, a changing magnification operation from the wide angle to thetelephoto is explained referring to the timing chart shown in FIG. 27.

By pressing down the zoom button, which is in a telephoto mode, thetelephoto switch signal changes from H to L, a variable sequence to thetelephoto direction is initiated. Initially, a retire determination ofthe fourth lens group 14 is executed (step S11).

As described above, in the retire determination of the fourth lens group14, the fourth lens group is retired only if the following conditionsare satisfied simultaneously (And).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a nearer position to thesubject or drawing out position away from a predetermined position orretired threshold position.

However, because the above-mentioned conditions are not satisfied in thedrive from the wide angle to the telephoto, the fourth lens group 14 isnot retired.

Next, the driving direction, whether the third lens group 13 is retiredis determined (step S12). In the case of the changing magnificationdrive from the wide angle to the telephoto, the retiring drive of thethird lens group 13 is not required. The drive of the first and secondlens groups 11 and 12 is initiated through the first and second framesDC motor 503 (step S13).

In an actuating period right after the initiation of actuation of thefirst and second frames DC motor 503, the drive voltage is set to belower than the stationary voltage in order to prevent an incomingcurrent by the first and second group DC motor. After the actuatingperiod is lapsed, the drive voltage is increased to the stationaryvoltage. The drive voltage between the wide angle and the telephoto isset to be lower than that between the collapsed position and wide angleposition. This is reason a higher speed is required between the storedand wide angle positions, hence a higher voltage is set and a suitablevoltage setting is made between the wide angle and the telephoto toallow the first and second frames DC motor 503 to stop at a desiredposition by operation of the zoom button.

The control of the moved amount of the first and second lens groups 11and 12 is achieved by counting the pulse-like signal or PI signal by thefirst and second frames photo-interrupter 509. The zooming points eachof which is a control reference position are set in 17 points in which adistance between the wide angle and the telephoto is divided into 16equally.

Next, whether the first and second lens groups 11 and 12 are stopped isdetermined (step S14). In the determination for stopping the drive ofthe first and second lens groups 11 and 12, if either one of thefollowing conditions is satisfied (OR), a stopping process is executed.

(1) A telephoto zooming drive switch operated by the changingmagnification operation through the zoom lever or zoom button or thelike is turned off, in other words, changed from L to H.

(2) The first and second lens groups reach a position in front of thetelephoto position when driving from the wide angle to the telephoto.

During the first and second lens groups 11 and 12 continue to drive, thedetermination of driving initiation/driving stop of the third lens group13 is executed in response to the status (during driving or stopping) ofthe third lens group 13 (step S23). If the third lens group 13 isstopping, the determination of drive initiation of the third lens group13 is executed (step S24), if the initiation is permitted, the drive ofthe third lens group 13 is initiated. In the step S24, the drive of thethird lens group 13 is initiated if either one of the followingconditions is satisfied.

(1) The first and second lens groups 11 and 12 are driven the specifieddriven amount or more after the initiation of the drive of the first andsecond lens groups.

(2) During the third lens group 13 is re-driving in the drive from thewide angle to the telephoto, the position of the third lens group 13 isaway by a predetermined amount from the position of the first and secondlens groups 11 and 12 when the first and second lens groups 11 and 12pass a predetermined zooming point.

Moreover, if the third lens group is driving, whether the third lensgroup 13 is stopped is determined (step S26), if the stop is permitted,the drive of the third lens group 13 is stopped. In the determinationwhether the third lens group 13 is stopped, the third lens group 13 isstopped if the following condition is satisfied.

The position of the third lens group 13 is positioned close than thepredetermine amount to the position of the first and second lens groups11 and 12 in the drive from the wide angle to the telephoto.

That is to say, the first and second lens group 11 and 12 are actuated,if the driven amount of the first and second lens groups 11 and 12becomes the specified pulse or more, the drive of the third lens group13 is initiated. During simultaneous drive of the first, second andthird lens groups, if the position of the third lens group 13 approachesby the predetermined amount to the position of the first and second lensgroups 11 and 12, the drive of the third lens group 13 is stopped.Thereafter, the first and second lens groups 11 and 12 are away from thethird lens group 13, if they are away from the third lens group 13 by apredetermined amount, the drive of the third lens group 13 isre-started.

The drive and stop of the third lens group 13 are repeated in responseto a positional relationship among the first and second lens groups 11and 12, and the third lens group 13. Thereby, it is possible to achievethe changing magnification drive while maintaining a distance among thefirst, second, and third lens groups 11, 12 and 13.

When actuating these lens groups, the influence of the incoming currentcan be avoided by initiating the drive of the third lens group 13 afterthe drive of the specified amount or more is carried out, therefore thecurrent consumption is reduced.

If the telephoto switch signal changes from L to H before the initiationof the initial drive of the third lens group 13, the stop of the firstand second lens groups 11 and 12 is controlled without the simultaneousdrive of the third lens group 13 therewith. If the first and second lensgroups 11 and 12 are stopped after the stop of them is determined, ifthe third lens group 13 is driving, the stop operation of the third lensgroup 13 is initiated. The stop of the first and second lens groups 11and 12 is also initiated. During the stop operation of the first andsecond lens groups 11 and 12, a lower speed control period is set, andthe drive voltage of the first and second frames DC motor 503 is lowereddepending on a residual pulse number to a target position.

Thereby, the overrun amount of the first and second lens groups whenreaching the target position is decreased. If the first and second lensgroups reach the target position by counting the PI signal by the firstand second frames photo-interrupter 509, a breaking operation isexecuted in order to stop the drive of the first and second lens groups11 and 12. A final position of the first and second lens groups 11 and12 is decided by further counting the overrun amount during the periodof breaking.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is configured to compute the stopping position of thethird lens group 13 corresponding to the final stopping position of thefirst and second lens groups 11 and 12 and drive the third lens group 13to the stopping position. A target stopping position of the third lensgroup 13 corresponding to the stopping position of the first and secondlens groups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups every the zooming pointand the positional information of the third lens group 13 every thezooming point. Thereafter, the drive of the aperture stop is achieved toset a position of the aperture stop corresponding to the stopped zoomingposition of the third lens group 13 (step S20).

[From the Telephoto to the Wide Angle]

Next, a changing magnification operation from the telephoto to the wideangle is described with reference to the timing chart shown in FIG. 28.

By pressing down the zoom button, which is in a wide angular mode, thewide angular switch signal changes from H to L, a variable sequence withrespect to the wide angular direction is initiated. Initially, a retiredetermination of the fourth lens group 14 is executed (step S1).

As described above, in the retire determination of the fourth lens group14, the fourth lens group is retired only if the following conditionsare satisfied simultaneously (And).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a closer position to thesubject or drawing out position away from a predetermined position orretired threshold position.

If the position of the fourth lens group 14 is in the nearer positionthan the predetermined position when driving from the telephoto to thewide angle. The retired amount is set to a range in which the third lensgroup 13 does not interfere with the fourth lens group 14 in thevariable operation of the third lens group 13.

Next, the third lens group 13 is retired. In order to prevent theinterference of the third lens group with the first and second lensgroups 11 and 12 depending on the drive of the first and second lensgroups 11 and 12, the third lens group 13 is driven previously by thespecified amount. The drive of the first and second lens groups 11 and12 is then initiated through the first and second frames DC motor 503.

As described above, in the actuating period right after the initiationof actuation of the first and second frames DC motor 503, the drivevoltage is set to be lower than the stationary voltage in order toprevent the incoming current by the first and second group DC motor.After the actuating period is lapsed, the drive voltage is increased tothe stationary voltage.

The control of the moved amount of the first and second lens groups 11and 12 is achieved by counting the pulse-like signal or PI signal by thefirst and second frames photo-interrupter 509. As described above, thezooming points each of which is a control reference position are set in17 points in which a distance between the wide angle and the telephotois divided into 16 equally.

In the determination for stopping the drive of the first and second lensgroups 11 and 12, if either one of the following conditions is satisfied(OR), the stopping process is executed, as described above.

(1) A telephoto zooming drive switch operated by the changingmagnification operation through the zoom lever or zoom button or thelike is turned off, in other words, changed from L to H.

(2) The first and second lens groups 11 and 12 reach a position in frontof the telephoto position when driving from the telephoto to the wideangle.

During the first and second lens groups 11 and 12 continue to drive, thedetermination of driving initiation/driving stop of the third lens group13 is executed in response to the status (during driving or stopping) ofthe third lens group 13. If the third lens group 13 is stopping, thedetermination for the initiation of drive of the third lens group 13 isexecuted, if the initiation is permitted, the drive of the third lensgroup 13 is initiated. In the determination for initiating the drive ofthe third lens group 13, the drive of the third lens group 13 isinitiated if either one of the following conditions is satisfied.

(1) The first and second lens groups 11 and 12 are driven the specifieddriven amount or more after the initiation of the drive of the first andsecond lens groups 11 and 12.

(2) During the third lens group 13 is re-driving in the drive from thetelephoto to the wide angle, the position of the third lens group 13approaches by a predetermined amount to the position of the first andsecond lens groups 11 and 12 when the first and second lens groups 11and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, the determination forstopping the drive of the third lens group 13 is executed, if the stopis permitted, the drive of the third lens group 13 is stopped. In thedetermination whether the third lens group 13 is stopped, the third lensgroup 13 is stopped if the following condition is satisfied.

The position of the third lens group 13 is away the predetermine amountor more from the position of the first and second lens groups 11 and 12in the drive from the telephoto to the wide angle.

That is to say, the first and second lens group 11 and 12 are actuated,if the driven amount of the first and second lens groups 11 and 12becomes the specified amount or more, the drive of the third lens group13 is initiated. During simultaneous drive of the first, second andthird lens groups 11, 12 and 13, if the position of the third lens group13 is away the predetermined amount from the position of the first andsecond lens groups 11 and 12, the drive of the third lens group 13 isstopped. Thereafter, the first and second lens groups 11 and 12 approachto the third lens group 13, if they approach to the third lens group 13the specified amount or more, the drive of the third lens group 13 isre-started.

The drive and stop of the third lens group 13 are repeated in responseto a positional relationship among the first and second lens groups 11and 12, and the third lens group 13. Thereby, it is possible to achievethe changing magnification drive while maintaining a distance among thefirst, second, and third lens groups 11, 12, and 13.

In actuating these lens groups, the influence of the incoming current ofthe first and second frames DC motor 503 can be avoided by initiatingthe drive of the third lens group 13 after the specified pulse or moreis counted, therefore the current consumption is reduced.

When the third lens group 13 is driven to the wide angular direction,during the drive of the first and second lens groups 11 and 12,basically a control for eliminating a backlash in the movement of thethird lens group 13 is required when it is stopped, but the control isnot carried out during the changing magnification operation toaccomplish a smooth movement of the third lens group.

If the wide angular switch signal changes from L to H before theinitiation of the initial drive of the third lens group 13, the stop ofthe first and second lens groups 11 and 12 is controlled without thesimultaneous drive of the third lens group 13 therewith. If the firstand second lens groups 11 and 12 are stopped after the stop of them isdetermined, if the third lens group 13 is driving, the stop operation ofthe third lens group 13 is initiated. The stop of the first and secondlens groups 11 and 12 is also initiated. During the stop operation ofthe first and second lens groups 11 and 12, a lower speed control periodis set, and the drive voltage of the first and second frames DC motor503 is lowered depending on a residual pulse number to a targetposition.

Thereby, the overrun amount of the first and second lens groups whenreaching the target position is decreased. If the first and second lensgroups reach the target position by counting the PI signal by the firstand second frames photo-interrupter 509, a breaking operation isexecuted in order to stop the drive of the first and second lens groups11 and 12. A final position of the first and second lens groups 11 and12 is decided by further counting the overrun amount during the periodof breaking.

Furthermore, a control for eliminating a backlash of the first andsecond lens groups 11 and 12 is executed in the movement from thetelephoto to the wide angle thereof.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is configured to compute the stopping position of thethird lens group 13 corresponding to the final stopping position of thefirst and second lens groups 11 and 12 and drive the third lens group 13to the stopping position. A target stopping position of the third lensgroup 13 corresponding to the stopping position of the first and secondlens groups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups every the zooming pointand the positional information of the third lens group 13 every thezooming point. In the drive in the wide angular direction of the thirdlens group 13, the control for eliminating the backlash of the thirdlens group 13 is executed after it is stopped. Thereafter, the drive ofthe aperture stop is achieved so that the aperture stop is disposed in aposition corresponding to the stopped zooming position of the third lensgroup 13.

In this example, the drive voltage of the first and second frames DCmotor 503 when it is driven in the wide angular direction is set to behigher than that in the telephoto direction in the changingmagnification operation between the wide angle and the telephoto. Thepulse rate of the third frame pulse motor 507 in the wide angulardirection is set to be faster than that in the telephoto direction. Anintermittent control for the third lens group 13 is accomplished basedon the positional relationship among the first, second, and third lensgroups 11, 12, and 13 in order to maintain the distance among the first,second, and third lens groups 11, 12, and 13. Therefore, the drive speedof the third lens group 13 is set to be the same as or faster than thedrive speed of the first and second lens groups 11 and 12, in themovement in the telephoto direction.

Similarly, the drive speed of the third lens group 13 is set to be thesame as or faster than the drive speed of the first and second lensgroups 11 and 12, in the movement in the wide angular direction. Withsuch a structure, the third lens group 13 is driven so that the thirdlens group 13 is not away a predetermined amount or more from the firstand second lens groups 11 and 12 in the movement in the telephotodirection, and does not contact with the first and second lens groups 11and 12 in the movement in the wide angular direction.

Moreover, although the driving re-start timing of the third lens group13 is set at the time of passing the predetermined zooming point in thisexample, the timing may be set every the time of detecting thepulse-like signal or PI signal by the first and second framesphoto-interrupter 509 generating in driving the first and second lensgroups 11 and 12, or every a predetermined count number of the PIsignal.

Thereby, it is possible to accomplish a further fine intermittentcontrol of the third lens group 13 and improve accuracy of the distanceamong the first, second and third lens groups.

In the above-mentioned embodiments, the structure in which the thirdlens group 13 can be retracted out the lens cylinder unit transverse tothe optical axis X has been described. In this structure, the retractedthird lens group has the minimum outer diameter. When the third lensgroup having the minimum outer diameter is retracted, a projective sizeof the lens barrel in which the third lens group is retracted can beminimized efficiently, and the thickness of the lens barrel can bereduced.

Moreover, when the retracted lens is extended out of the fixed frame, asize of the device (lead screw and so on) for driving the retired lensgroup or the third lens group is minimized by taking a structure suchthat the retracted lens is not way from the imaging plane possibly.

Furthermore, the lens retaining frame of the third lens group 13 or thethird lens group 13 itself is larger than the lens retaining frames ofthe other lens groups 11, 12, 14 or the other lens groups 11, 12, 14 inlength along the optical axis X, in other words, thickness.

When the thickness of the third lens group 13 is larger than that of theother lens groups 11, 12, and 14, consequently, the thickness of theother lens groups decreases, therefore, the thickness of the lens barrelcan be reduced when the lens barrel is in the collapsible position.

As a result, the thickness of the lens barrel or a size in the directionof the optical axis of the lens barrel is minimized.

Because the retract lens group or the third lens group 13 is disposedbehind and adjacent the shutter having the aperture stop function, thediameter of the lens barrel is less, and the retraction of the thirdlens group is simplified without considering the interference of theshutter with the lens group unit and separating the position of theshutter from the lens cylinder unit, excessively.

Next, a structure of the plurality of lens groups is explained infurther detail.

The first lens group 11 has a positive power, the second lens group 12has a negative power, the third lens group 13 has a positive power, andthe fourth lens group 14 has a positive power. A changing magnificationoperation is achieved by changing at least one of intervals between thefirst and second lens groups 11 and 12, between the second and thirdlens groups 12 and 13, and between the third and fourth lens groups 13and 14. A focusing operation is achieved by moving the fourth lens group14 along the optical axis X.

The shutter/aperture unit 15 is disposed between the second lens group12 and the third lens group 13. In other words, the shutter having thefunction of the aperture stop is positioned in front of the third lensgroup 13. The four lens groups are provided in the lens cylinder unit.Because the third lens group having the minimum outer diameter isretracted out of the lens cylinder unit without separating from theimage plane excessively, the retraction of the third lens group 13 canbe accomplished with the minimum movement and the outer diameter of thelens barrel can be minimized. In addition, the thickness of the lensbarrel is decreased by retraction of at least one lens group.

Furthermore, it is possible to provide a compact lens barrel having ahigh changing magnification ratio, 4 times or more.

Meanwhile, the lens groups may be structured from a first lens grouphaving a positive power, a second lens group having a negative power,and a third lens group having a positive power, and the third lens groupmay be retracted.

Alternatively, the lens groups may be structured by a first lens grouphaving a negative power, a second lens group having a positive power,and a third lens group having a positive power, and the second lensgroup or the third lens group may be retracted.

Each of the lens groups may be structured from one or more lenses, andthe lens groups herein indicate integral one or more lenses. Therefore,all the lens groups may be structured by one lens, respectively.

Referring now to FIG. 17 to FIG. 19, a camera including an opticalsystem device having the lens barrel according to the present inventionas shown in the first embodiment will be described.

Although the lens barrel is applied to the camera here, the lens barrelis also used to a portable information terminal such as so-called PDA(Personal Data Assistant) or a mobile phone, having a camera function orfunctional part installed therein.

Many of such portable information terminals have the function and thestructure substantially identical to the function and the structure ofthe camera, although the appearance is slightly different, and hence theoptical system device including the lens barrel according to the presentinvention may be employed in such mobile information terminals. Further,the lens barrel according to the present invention may be applied to animaging device such as a copying machine, a scanner or the like.

As shown in FIG. 17 and FIG. 18, the camera includes an image pickuplens 101, a shutter button 102, a zoom lever 103, a finder 104, a strobelight 105, a liquid crystal display (=LCD) 106, an operating button 107,a power switch 108, a memory card slot 109, an expansion card slot 110,the barrier-operating element 301 and so on.

Furthermore, as shown in FIG. 19, the camera also includes aphotodetector 201, a signal-processing unit 202, an image-processingunit 203, a central processing unit (CPU) 204, a semiconductor memory205, and an expansion card 206. Although it is not shown clearly,electric power is supplied from a battery as an electric source to theabove-mentioned parts to operate the parts.

The photodetector 201 serves as an area sensor such as a CCD (chargecoupled device) image pickup element or the like to read an image of asubject to be photographed, that is, of an photographing subject, formedby the image pickup lens 101, which is a photographing optical system.As the image pickup lens 101, the optical system device including thelens barrel according to the present invention as described in the firstembodiment is employed.

More specifically, the optical system device includes a plurality lensgroups as optical elements and a telescopic cylinder unit retaining thelens groups, which constitute the lens barrel.

The lens barrel has a mechanism of retaining the respective lens groupsin the lens cylinder such that the lens groups can be moved in responseto the movement of the lens cylinder along the optical axis of the lensgroups, similarly to the above-mentioned embodiment. The image pickuplens 101 to be integrated in the camera is generally integrated in theform of this optical system device.

An output from the photodetector 201 is processed by thesignal-processing unit 202, which is controlled by the centralprocessing unit 204, and is converted into digital image information.The image information digitized by the signal-processing unit 202 issubjected to a predetermined image processing in the image-processingunit 203 which is also controlled by the central processing unit 204,and then stored in the semiconductor memory 205 such as a non-volatilememory.

In this case, the semiconductor memory 205 may be a memory card insertedin the memory card slot 109, or may be a semiconductor memory integratedin a body of the camera. The liquid crystal display (=LCD) 106 maydisplay the photographing image or may display the image stored in thesemiconductor memory 205. An image stored in the semiconductor memory205 can be transmitted to the outside of the camera via the expansioncard 206 inserted in the expansion card slot 110. Meanwhile, theabove-mentioned central processing unit (CPU) 501 shown in FIG. 21 tocontrol the drive of the lens groups may be included in the centralprocessing unit 204, otherwise structured by use of othermicro-processor connecting with the unit 501.

The image pickup lens 101 is embedded within the camera body into acollapsed or stored state as shown in FIG. 17A when being transported,and the lens barrier 62 is also into a closed state. When a useroperates the barrier-operating element 301 and opens the lens barrier62, the power is turned on and the lens barrel is moved from the closedposition to an opened position and projected from the camera body asshown in FIG. 17B, so that the photographing state is established. Atthis time, the image pickup lens 101 within the lens barrel is set sothat the respective lens groups of the optical systems constituting azoom lens are arranged, for example, at a short focal length/wide angleposition.

When the zoom lever 103 is operated, the arrangement of the respectivelens groups in the optical system is changed through the movement of thelens groups along the optical axis, therefore, the zoom can be varied tothe telephoto position.

Preferably, an optical system of the finder 104 is configured such thatthe zooming is varied in association with the change of the angle offield of the image pickup lens 101.

In many cases, focusing is achieved by half-pressing operation of theshutter button 102. The focusing with the zoom lens in the lens barrelaccording to the present invention is achieved mainly by moving thefourth lens group 14. When the shutter button 102 is further pressed toa completely pressed state, the photographing is achieved, andsubsequently the processing as described above is performed.

In order to display the image stored in the semiconductor memory 205 onthe liquid crystal display (=LCD) 106 or transmit the same to theoutside of the camera via the expansion card 206, the operating button107 is operated in a predetermined manner. The semiconductor memory 205and the communication card 206 or the like are used by being inserted ina specific or multi-purpose slot such as the memory card slot 109 andthe communication car slot 110.

When the image pickup lens 101 is in the stored state, the third lensgroup 13 is retracted out of the optical axis, and hence is stored in aline with the first lens group 11 and the second lens group 12 in ajuxtaposed manner. Therefore, further reduction in thickness of thecamera is achieved.

Generally, because a finder mechanism is disposed above of the lensbarrel, therefore, certain camera operation is easy. Moreover, if thelens barrel includes a zoom changing magnification mechanism, becausethe finder mechanism also needs the zoom changing magnificationmechanism, it is preferable that a drive source (DC motor, pulse motoror the like) for conducting the zoom changing magnification operationand a transmission mechanism (gear connecting mechanism or the like) fortransferring a driving force of the drive source to the lens groups aredisposed adjacent the finder mechanism. For example, if the findermechanism is disposed on upper and left position of the lens barrel, thedrive source and the transmission mechanism are disposed adjacent theupper and left position of the lens barrel to use a limited spaceeffectively.

Next, the frame 31 for the retractable lens group or third lens group 13is retracted, the retaining frame is stored below the lens barrel inconsideration of the left space. The space is lower and right positionor lower and left position of the lens barrel. In the embodiment, thespace is disposed on the lower and right position of the lens barrel tostore the retaining frame of the retracted third lens group. Theabove-mentioned storage part of the fixed lens cylinder is disposed atthe position.

The drive source and the transmission mechanism for driving the lensgroups are disposed at the lower and left position. As a result, aminiaturized lens barrel can be accomplished with effective use offourth corners, the upper and left position, the upper and rightposition, the lower and right position, and the lower and left positionof a usual circular lens barrel.

Although the present invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly to include other variants and embodiments ofthe invention which may be made by those skilled in the field of thisart without departing from the scope and range of equivalents of theinvention.

1. A lens barrel, comprising: a telescopic cylinder configured to be accommodated within a fixed cylinder; a plurality of lenses configured to be retained in the telescopic cylinder; a plurality of lens retaining frames, each lens retaining frame configured to retain at least one lens in the plurality of lenses; a lens driving device configured to drive the plurality of lens retaining frames so as to drive the plurality of lenses along a longitudinal axis of the telescopic cylinder; at least one retractable lens configured to be retracted into the fixed cylinder through an opening in a wall of the fixed cylinder when the telescopic cylinder is extended out of the fixed cylinder; a retractable lens retaining frame configured to retain the at least one retractable lens, wherein the lens driving device is configured to drive the retractable lens retaining frame so that the retractable lens is retracted onto an optical axis of the lenses when the telescopic cylinder is extended out of the fixed cylinder.
 2. The lens barrel according to claim 1, further comprising: an extended state retention member, wherein if the plurality of lenses are in extended positions and an external impact is received by the lens barrel, the extended state retention member is configured to abut against at least either one of the plurality of lens retaining frames or the telescopic cylinder to prevent the plurality of lens retaining frames from moving toward the collapsed state and contacting the retractable lens retaining frame by a force of the external impact.
 3. The lens barrel according to claim 2, wherein the extended state retention member is configured to be pressed by the retractable lens retaining frame when the retractable lens retaining frame is retracted out; and the extended state retention member is configured to be released from being pressed by contact with the retractable lens retaining frame and to be moved to a position capable of abutting against at least either one of the plurality of lens retaining frames or the telescopic cylinder when the plurality of lenses are in the extended position in which the retractable lens retaining frame is inserted into the fixed cylinder and positioned on the optical axis and an external impact is received by the lens barrel.
 4. The lens barrel according to claim 1, wherein the extended state retention member is configured to be biased toward a direction in which the extended state retention member is in a position corresponding to the extended position of the plurality of lenses.
 5. The lens barrel according to claim 3, wherein the extended state retention member is configured to be biased toward a direction in which the extended state retention member is in a position corresponding to the extended position of the plurality of lenses.
 6. A camera comprising a photographing optical system including the lens barrel recited in claim
 1. 7. A camera comprising a photographing optical system including the lens barrel recited in claim
 2. 8. A camera comprising a photographing optical system including the lens barrel recited in claim
 3. 9. A camera comprising a photographing optical system including the lens barrel recited in claim
 4. 10. A camera comprising a photographing optical system including the lens barrel recited in claim
 5. 11. A portable information terminal, comprising: a camera functional unit, the camera functional unit including a photographing optical system including the lens barrel according to claim
 1. 12. A portable information terminal, comprising: a camera functional unit, the camera functional unit including a photographing optical system including the lens barrel according to claim
 2. 13. A portable information terminal, comprising: a camera functional unit, the camera functional unit including a photographing optical system including the lens barrel according to claim
 3. 14. A portable information terminal, comprising: a camera functional unit, the camera functional unit including a photographing optical system including the lens barrel according to claim
 4. 15. A portable information terminal, comprising: a camera functional unit, the camera functional unit including a photographing optical system including the lens barrel according to claim
 5. 